Power over Ethernet (PoE), in accordance with both IEEE 802.3af-2003 and IEEE 802.3at-2009, each published by the Institute of Electrical and Electronics Engineers, Inc., New York, the entire contents of each of which is incorporated herein by reference, defines delivery of power over a set of 2 twisted wire pairs without disturbing data communication. The aforementioned standards particularly provide for a power sourcing equipment (PSE) and a powered device (PD). The power sourcing equipment is configured to detect the PD by ascertaining a valid signature resistance, and to supply power over the 2 twisted wire pairs only after a valid signature resistance is actually detected.
The HD BaseT Alliance of Beaverton, Oreg. has published the HDBaseT Specification Version 1.1.0 which defines a high power standard utilizing twisted wire pair cabling, such as Category 5e (CAT 5e) or Category 6 (CAT 6) structured cabling as defined by ANSI/TIA/EIA-568-A. The specification provides for even higher power than the above mentioned IEEE 802.3at-2009 over each set of 2 pairs, with all 4 pairs utilized for powering, and allows for power over structured communication cabling from any of: a type 1 PSE, denoted hereinafter as a low power PSE, typically meeting the above mentioned IEEE 802.3af standard; a type 2 PSE denoted hereinafter as a medium power PSE, typically meeting the above mentioned IEEE 802.3at standard; a type 3 PSE, denoted hereinafter as a high power PSE, typically meeting the above HDBaseT specification; twin medium power PSEs; and twin high power PSEs.
In the PoE process, a valid device detection is first performed. This detection process identifies whether or not the PSE is connected to a valid PD to ensure that power is not applied to non-PoE capable devices. After a valid PD is discovered, the PSE can optionally perform a power classification. For example, in the IEEE 802.3af standard, the classification step identifies a power classification of the PD from among a variety of power classes. After the classification process is complete, the PSE is arranged to allocate power to the port in accordance with the power classification. Particularly, the PSE is arranged to provide power to a detected PD only if it is determined that enough power, as indicated by the classification, is available to be allocated.
Recently, an interest has developed to utilize PoE to power lighting systems. One disadvantage of powering lighting systems with PoE is the amount of time the PoE system takes to restart after a power outage. Particularly, a 24 port PoE hub can take up to 15 seconds to start up all ports, including the detection and classification stages, which is an extremely long amount of time for lighting systems.